proximal sigmoid colon

AT my last years colonoscopy the gi told me my colitis goes up to 50cm,just last week called and asked to have the report send to me .Received it today and it states" higher up the proximal sigmoid colon and descending colon shows no evidence of inflammation.The sigmoin is only about 35-40cm long and the rectum 15 cm long so how can it be 50cm affected.I am confused!! Any help appreciated!!